Heavy fog prevents mosquitoes from flying

Collision with haze drops immobilizes the position sensor of the insects

In the fog, mosquitoes can not fly. © George Shuklin / CC_by-sa 3.0
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The collision with a raindrop easily survives a mosquito, but in the fog it gets problems: The countless tiny fog droplets block their vibrating cup - two small, behind the wings seated position sensors. This is what US researchers discovered using high-speed images. Thus, the oscillating sensors collide with thousands of droplets of mist every second and thus do not work properly anymore. As a result, the mosquito can no longer determine their body position in flight and lose their stable attitude, the scientists report on Monday at a physics conference in San Diego, California.

"Mosquitoes are good flyers even in the rain, but in fog they can not, " write Andrew Dickerson and his colleagues at the Georgia Institute of Technology. A raindrop is about 50 times the size of a mosquito, a collision therefore comparable to the collision of a person with a bus. Although the tiny insect collides with a drop every 20 seconds during a downpour on average, it survives without damage and continues to fly. "Heavy fog, on the other hand, consists of droplets that are 100 times smaller than in the rain, but the mosquito can not fly under these conditions, " the researchers write. Similar to modern airplanes, the insect must remain on the ground in heavy fog. Why, was so far unclear.

Mosquito test flight in the cloud chamber

To find out why mosquitoes can not fly in fog, the researchers placed mosquitoes individually in a small flight cage that stood in a cloud chamber. With a special camera for high-speed recordings they filmed their wing movements, body position and the movements of the vibrating calves. The evaluation of the pictures showed that the mosquito can beat its wings even in heavy fog - albeit slower than normal. But that's enough to give enough lift to fly, the scientists say. Therefore, the mere weight of the mist drops that hit the body and wing is not the reason for the flight problems. "A fog droplet weighs 20 million times less than a mosquito, " the researchers explain. If the mosquito gets hit by such a droplet, do not do it worse than throwing a breadcrumb.

In the high-speed shots, however, the researchers discovered another reason for the fly problems of the mosquito: The fog impaired the function of the vibrating calves. These sensors, developed from the rear wings, sit behind the forewings and swing with them in time, but in opposite directions: If the wings go up, they swing down and vice versa. By means of tiny changes in these approximately 400 vibrations per second, the feet can close their physical position in the room.

The experiment showed that these tiny sensors in fog constantly collide with the roughly equivalent fog droplets - thousands of times a second, as the researchers report. Normally these sensors, which are also referred to as holders, are water-repellent, but this repeated collision disturbs their vibrations and thus hinders the position control of the mugs in flight. "Like airplanes, insects can not fly when they can no longer see their surroundings, " explains Dickerson. In the case of human pilots, the fog obstructs above all the view that he is taking the position sensor. display

(American Institute of Physics, 20.11.2012 - NPO)